The present invention relates to the maintenance of water percolation basins. A water percolation basin is a large, man-made basin created for the purpose of capturing water such as, for example, rainwater, recycled water and/or run-off from melting snow in the mountains. These basins are particularly important in dry and/or arid portions of the country, such as Southern California. These basins range in size from several acres to several hundred acres. The purpose of the basin is not only to capture water but primarily to allow the water to percolate down through the floor of the basin and into the underground water table. The water may thereafter be pumped out of the recharged water table by various systems known in the art. The need for additional sources of water is overwhelming and does not require elaboration.
The primary problem encountered with these percolation basins is that relatively thin layers of silt or clay accumulate on the floor of the basin and dramatically reduce the ability of the water to penetrate the floor of the basin and percolate downwardly into the water table. Various efforts have been made to remove such layers to rehabilitate the percolation capacity of the floor of these basins. Unfortunately, the prior art efforts have been completely unsatisfactory and have been very expensive.
One typical prior art method requires simply waiting until the basin is dry and entering the basin with rather large machines to mechanically remove the silt or clay layer build-up from the floor of the basin. This technique is very expensive and the basin only percolates effectively for a short time.
The prior art also includes the Clark et al U.S. Pat. No. 6,017,400 for cleaning a water basin floor. Clark et al teaches a system wherein a series of water jets hydraulically agitates and fluidizes the layer of unwanted silt along with some of the porous sand underneath the silt. The fluidized silt and sand mixture is drawn upwardly through a relatively large, inclined separation chamber in which the larger sand particles are separated by gravity from the smaller silt particles. The sand particles are returned to the basin floor and the silt particles are removed from the basin.
The applicants have observed the apparatus taught by Clark et al and believe it is unsatisfactory for use in many, if not most, percolation basins for several reasons. First, the objective of separating sand from silt using gravity requires a relatively large separation chamber, which in turn limits the vacuum obtainable for removing silt particles. Secondly, the use of high pressure water jets to hydraulically agitate and fluidize the silt layer along with an underlying layer of sand will not perform well where the silt is relatively thick and dense, such as a layer of aluminum silicate clay with a thickness of 4 mm. or more. The thicker and denser the layer of silt, the less able the water jets are to agitate and fluidize the silt. If the water jet pressure is increased to penetrate a thick, dense layer of silt, an inherent result is to cause “potholes” in the basin floor, a result that is wholly unacceptable.
The present invention, in contrast to Clark et al, does not separate sand from silt and is therefore able to avoid a separation chamber and to use a much smaller underwater vehicle (less than 1% of the size of Clark et al) capable of generating a much larger vacuum adjacent the layer of silt. In further contrast to Clark et al, the present invention does not hydraulically agitate and fluidize the silt, but rather mechanically cuts and/or lifts the silt layer and then applies a large vacuum to remove the fragmented, non-fluidized silt from the basin.
A primary object of the present invention is to provide a method and apparatus for efficiently and effectively removing accumulated silt from the floor of a water percolation basin.
A further object of the invention is to provide a method and apparatus for removing accumulated fatty clay such as aluminum silicate, from the floor of a water percolation basin wherein the clay is cut and/or lifted by blades to form fragments which are immediately vacuumed and removed from the basin floor.
A further object of the invention is to provide a method and apparatus for cleaning accumulated silt from a water percolation basin floor wherein a remotely controlled underwater terrain vehicle performs the cleaning and utilizes an onboard side scanning sonar for guidance purposes.
A further object of the invention is to provide a method and apparatus for removing accumulated silt from a water percolation basin floor wherein a remotely controlled underwater terrain vehicle is equipped with an eductor driven vacuum head together with first and second rows of blades carried on either side of said vacuum head, allowing the UTV to clean the basin by moving forwardly to form a first swath and backwardly (or in reverse) to form an adjacent second swath so that the UTV does not have to make a series of 180° turns.
Further objects and advantages of the invention will become apparent from the following description and drawings wherein: